Filter membrane module, and method for its production

ABSTRACT

The invention relates to a method for producing a membrane module, comprising a plurality of elongated filter elements disposed in parallel adjacent to one another, each element comprising a longitudinal channel, a housing enclosing the filter elements, and a collector chamber between the housing and the filter elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/EP2011/052074 filed on Feb. 11, 2011, which claims the benefit of DE10 2010 008 869.2, filed Feb. 22, 2010, and DE 20 2010 005 971.2, filedApr. 22, 2010. The disclosures of the above applications areincorporated herein by reference.

FIELD

The present disclosure relates to a filter membrane module and a methodfor producing a filter membrane module.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

One such membrane module includes an elongated filter element, which ispenetrated by at least one longitudinal conduit and comprises a porousmaterial, such as ceramic. The module further includes a housing, whichsurrounds the filter element and with it forms a collection chamber.

Such a module functions as follows: Into one end of each longitudinalconduit, the medium to be treated, the so-called unfiltrate, isintroduced. Along the course of the unfiltrate, filtrate passes throughthe wall surface of the longitudinal conduit, enters the aforementionedcollection chamber between the filter element and the housing, and iscarried away from there as filtrate. The unfiltrate emerges from theother end of the longitudinal conduits and is optionally returned to thefirst end of the longitudinal conduit, so as to form a cycle. The wallsurfaces of the longitudinal conduits are coated with a material that isalso permeable to a certain extent. This usually very thin film usuallyforms the actual filtration device.

A single filter element has a plurality of longitudinal conduits(multi-conduit element). A plurality of such multi-conduit elements iscombined to form a membrane module from them.

On each face end of the filter elements, there is a face-end plate. Itdefines the annular chamber between the housing and the filter elements,specifically in such a way that the annular chamber is sealed off fromthe outer environment at least in fluid-tight fashion. Sealing it offcan be problematic, since during operation varying temperatures prevail,which lead to expansion and contraction of structural parts, in fact indifferent ways. The face-end boundary plates may for instance be ofspecial steel.

Exemplary embodiments have become known from EP 0 270 051 B1 and DE 69019 552 T2. EP 1 374 979 A2 describes a filter membrane module having amultitude of spaghetti-type individual filter capillaries, which arebundled at theirs ends by means of a potting material. DE 600 24 966 T2discloses a thermoplastic filter cartouche with a plurality ofconcentric filter tubes. US 2008/0035270 A1 relates to a filter membranemodule having a multitude of fibers, the ends of which are bundled bymeans of a potting material. US 2007/0144716 A1 describes a device withporous membranes, the ends of which being unitarily combined by potting.

SUMMARY

The object of the invention is to provide a filter membrane modulehaving a high filter performance and offering more simple and thuscheaper manufacturing.

This object is attained by the features of the independent claims.

One fundamental concept of the invention is that a plastic pottingmaterial, such as a thermoplastic, in particular a polymer, is appliedto the end region of the filter elements. The plastic thus blocks offthe interstices between the filter elements. It forms a mounting ring,which in turn surrounds the filter elements in their end region.

The term “plastic” should be understood in the broadest sense. Forinstance, thermoset plastics or dual-component plastics such as epoxiesor acrylates can be considered.

This method is performed on both ends of the bundle of filter elements,so that two mounting rings are created. Then the housing is slipped ontoboth mounting rings and thus onto the filter element bundle.

In an inventive multi-conduit element, a mounting ring, again comprisinga plastic potting material, is first applied to one end and then to theother end of the filter element. After the application, in both casesthe plastic potting material is made to harden. The same is done on theother end. Then the housing is again slipped onto the two mountingrings.

Flat membranes can be manufactured at low cost. By means of the flat andlarge interstices formed between the filter elements, the filtrate canbe bled off very efficiently.

The housing can be formed of the same material as the mounting rings.The housing can even be in one piece with one of the two mounting rings,by being produced in a single potting operation.

In filter devices of the aforementioned structural type with ceramicfilter elements, one known problem is the variably pronounced expansionunder the influence of heat. This problem arises when materials withdifferent coefficients of thermal expansion are used.

It is therefore recommended that the bearing of the housing on at leastone of the mounting rings be embodied as a loose bearing, so thatimpermissible thermal stresses do not occur between the ceramic part andthe housing.

The housing can be provided with connections for supplying or removingmedium, for example for the medium to be treated (so-called unfiltrate)or for the treated medium (filtrate). If the housing is made fromthermoplastic material, then potting the connection ports integrallywith it is an attractive option.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 shows a single hollow ceramic fiber (spaghetti) in perspective.

FIG. 2, in an axially vertical cross section, shows three pieces ofspaghetti filter elements combined in a bundle.

FIG. 3 shows a bundle of spaghetti filter elements surrounded by asleeve.

FIG. 4 schematically shows the subject of FIG. 3, with one end dippedinto a tub that contains a potting material.

FIG. 5 shows the bundle with the sleeve of FIG. 3 after the pottingmaterial has hardened.

FIG. 6 shows the end region of a multi-conduit element in perspective.

FIG. 7 shows the subject of FIG. 6, provided with a mounting ring.

FIG. 8 shows the complete filter device in an elevation view and partlycut away, including a plurality of filter elements in one housing.

FIG. 9 shows a further filter apparatus in an elevation view and partlycut away.

FIG. 10 shows the apparatus of FIG. 9 in a plan view.

FIG. 11 shows an embodiment of an inventive filter device in crosssection, with five flat membranes.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features. Itshould also be understood that various cross-hatching patterns used inthe drawings are not intended to limit the specific materials that maybe employed with the present disclosure. The cross-hatching patterns aremerely exemplary of preferable materials or are used to distinguishbetween adjacent or mating components illustrated within the drawingsfor purposes of clarity.

A spaghetti element 1 shown in FIG. 1 is of ceramic. It surrounds alongitudinal conduit 1.1. The spaghetti bundle shown in FIG. 2 includesthree pieces of spaghetti 1, each with a longitudinal conduit 1.1. Thethree pieces of spaghetti enclose a hollow space 1.2 between them.

FIG. 3 shows a bundle of spaghetti 1 surrounded by a sleeve 2. Thesleeve 2 has a plurality of openings 2.1, so that there is a conductiveconnection between the hollow spaces 1.2, each located between pieces ofspaghetti 1 adjacent one another, and the external environment.

FIG. 4 schematically illustrates the application of a mounting ring3—see also FIG. 5. For that purpose, the subject of FIG. 3 is dipped byone of its ends into a potting material 4, which is located in a tub 5.The potting material 4 comprises plastic, such as a thermoplasticmaterial, or synthetic resin. After the subject of FIG. 3 has beendipped, the potting material penetrates through the openings 2.1 intothe hollow spaces 1.2 in the spaghetti 1 and fills them up. After thepotting material has hardened, the result is the subject shown in FIG.5, that is, the spaghetti bundle, surrounded by the sleeve 2, with themounting ring 3.

For the filtration process, it is necessary that the longitudinalconduits 1.1 remain open. This can be achieved in various ways. If thelower end face of the bundle is absolutely flat and flush with thebottom of the tub 5, then the penetration of potting material into thelongitudinal conduits 1.1 can be prevented. The ends of the longitudinalconduits 1.1 could also be provided with plugs, but this is tedious andexpensive. Finally, after the state shown in FIG. 5 is reached, thebundle can be shortened, by cutting off a desired piece at its lowerend, since because the diameter of the longitudinal conduits is soslight, the potting material does not penetrate them overly much.

FIG. 6 shows the end region of a multi-conduit element 6 having aplurality of longitudinal conduits 6.1. The element 6 is of ceramic. Itis hexagonal in cross section. Still other cross sections are alsopossible here, such as round or oval ones.

The application of mounting rings is done for the multi-conduit elementin precisely the same way as for the spaghetti element. See FIGS. 4 and5. However, what is crucial here is solely the application of themounting ring 3. Conversely, it is no longer crucial to fill up hollowspaces analogously to the hollow spaces 1.2 in the bundle shown in FIG.2.

In each case, the mounting rings 3 are seated solidly on the spaghettibundle, or on the multi-conduit element. Now a union with a housing mustbe established. The finished filter apparatus is seen in FIG. 8. In it,a plurality of multi-conduit elements 6 are surrounded by a housing 7.Instead of the multi-conduit elements 6, spaghetti elements could alsobe provided.

The housing 7 in the embodiment shown comprises a thermoplasticmaterial. This is the same material that comprises the mounting ring 3.The housing 7 and mounting ring 3 are produced in a single pottingoperation and are thus in one piece. This is true in any case for thelower mounting ring 3.1, which in a sense forms the bottom of thehousing 7. It does not apply to the upper mounting ring 3.2, however.There is a seam between it and the upper end of the housing, so that anaxial relative motion between the upper mounting ring 3.2 and thehousing 7 is possible. It is thus also ensured that during the operationof the filter apparatus, the housing 7 can expand to different extentscompared to the structural parts surrounded by the housing, namely themulti-conduit elements 6.

At this point, however, a seal is required. See the O-ring 8. This ringis let into the outer circumference of the upper mounting ring 3.2. Itcan already be potted integrally with the mounting ring 3.2 in theoperation of potting the mounting ring.

The individual multi-conduit elements 6 are surrounded by a collectionchamber 9.

The housing 7 includes a lower cap 7.1 and an upper cap 7.2. Twoconnection stubs, namely a lower connection stub 7.3 and an upperconnection stub 7.4, are also formed integrally with the cylindricalpart of the housing.

The filter apparatus of FIG. 8 functions as follows:

Through the lower cap 7.1, medium to be filtered (unfiltrate) flows tothe lower face ends of the multi-conduit elements 6. There, it entersthe longitudinal conduits 6.1 and flows through them. It then emergesfrom the upper ends of the longitudinal conduits 6.1 and reaches theupper cap 7.2.

Over this course, filtrate passes crosswise to the flow direction intothe longitudinal conduits 6.1 through the porous ceramic material of theindividual multi-conduit element 6 and reaches the collection chamber 9.From there, it reaches the lower outlet 7.3 and the upper outlet 7.4.

In a known manner, the unfiltrate entering the upper cap 7.2 can becarried in circulatory fashion and delivered to a further filterapparatus, or the same one, where it passes through further filtrationoperations.

The filtration apparatus shown in FIGS. 9 and 10 again has a housing ofa thermoplastic material. The filter elements 1 are of the spaghettitype.

An alternative embodiment of a filtration apparatus, shown in FIG. 11,has a housing, not shown in this drawing, similar to that of FIGS. 9 and10. However, the multi-conduit elements are not round (“tubularmembrane”) but instead are embodied in the form of five elements 6 a-6e, all of them flat (“flat membranes”) between which shallow, wideinterstices 10 are present. The flat membranes 6 a and 6 e and the flatmembranes 6 b and 6 d are embodied identically, but are disposedmirror-symmetrically to one another. Overall, the outer contours of theflat membranes 6 a-6 e are adapted to insertion into the tubularhousing. It is understood that in other embodiments, not shown, adifferent number of flat membranes can also be used.

The cross sections of the two outer flat membranes 6 a and 6 e are inthe form of classical circular segments, which are bounded on one sideby a circular arc and on the other by a chord. The inner flat membranes6 b, 6 c and 6 d are each bounded by two circular arcs and two chords.The height h of all five flat membranes 6 a-6 e is identical. For thesake of simplicity, the height is shown in FIG. 11 only for the upperflat membrane 6 b in FIG. 11. Here again, it is understood that in anembodiment that is not shown, still other cross sections, such as ovalor even free-form cross sections, can also occur. In each flat membrane6 a-6 e, there are many longitudinal conduits 6.1, of which for the sakeof simplicity only one is provided with a reference numeral in FIG. 11.In the present instance, the longitudinal conduits 6.1 have anapproximately square cross section, but they can have a different crosssection instead.

The production and material of the embodiment of FIG. 11 are identicalto the foregoing embodiments. First, the flat membranes 6 a-6 e aredisposed in the desired manner and at the desired spacing from oneanother. Then the axial ends of the flat membranes 6 a-6 e are pottedwith a plastic material, as shown as an example in conjunction with adifferent exemplary embodiment in FIGS. 4 and 5 and described above withreference to them. The result on the axial ends is equivalent mountingrings, of which only one mounting ring 3.1 on the end is visible in FIG.11. The plastic material on the axial ends of the flat membranes 6 a-6 eis also present in the interstices 10, and as a result, they areproduced reliably and durably.

The function is also essentially equivalent to the function that hasalready been described above in conjunction with the tubular membranes6: While the medium to be filtered is being conducted through thelongitudinal conduits 6.1, the filtrate is conducted away via theinterstices 10 and the interstice, between the housing and the flatmembranes 6 a-6 e, that is formed by the mounting ring 3.1.

The description of the disclosure is merely exemplary in nature and,thus, variations that do not depart from the substance of the disclosureare intended to be within the scope of the disclosure. Such variationsare not to be regarded as a departure from the spirit and scope of thedisclosure.

What is claimed is:
 1. A filter membrane module, including: a pluralityof elongated filter elements, which each have a plurality oflongitudinal conduits; and a housing surrounding the filter elements;wherein the filter elements are potted in both of their end regions witha material, which forms after hardening a mounting ring surrounding theplurality of filter elements; wherein either the housing is slipped overthe mounting ring and sealingly joined to it or is unitary with one ofthe two mounting rings by being manufactured in a single pottingoperation, wherein the filter elements are formed as flat membranes,which preferably have a segment of a circle type cross section, betweenwhich flat and large interstices are provided, and in that the wallsurfaces of the longitudinal conduits are coated with a filtrationmaterial such that the medium to be filtrated can be conducted throughthe longitudinal conduits and the filtered medium can be dischargedthrough the interstices and a collecting space which is formed by meansof the mounting ring between housing and the flat membranes.
 2. Thefilter membrane module according to claim 1, wherein the housingcomprises a plastic, for instance thermoplastic, a thermoset plastic ora dual-component plastic, such as epoxy or acrylate.
 3. The filtermembrane module according to claim 1, wherein the housing has oneconnection each for the unfiltrate and for the filtrate.
 4. The filtermembrane module according to claim 1, wherein three sealing elements arepotted integrally with the mounting rings.
 5. A method for producing afilter membrane module according to claim 1, wherein the methodcomprises: applying a potting material of plastic, in particular athermoplastic, a thermoset plastic or a dual-component plastic such asan epoxy or acrylate, to one end region of the plurality of filterelements such that it sheathes the filter elements on their ends andthereby forms a mounting ring; hardening the potting material; doing thesame to the other end; if necessary: slipping the housing over themounting rings; sealing off the mounting rings from the housing.
 6. Themethod according to claim 5, wherein the end regions of the filterelements are dipped into the potting material.
 7. The method accordingto claim 5, wherein a sleeve is used for forming the mounting rings. 8.The method according to claim 5, wherein at least the jacket faces ofthe mounting rings are mechanically machined.
 9. The method according toclaim 5, wherein at least one sealing ring each is potted integrallyinto a mounting ring.